#!/usr/bin/perl
use warnings;
my $s='the quick red fox';
print $s, "\n";
my $s='Foo';
print $s, "\n";
{
    my $s="Bar";
    print $s, "\n";
    my $s;
    print $s, "\n";
}
print $s, "\n";

##</code><code>##

$ perl t.pl
"my" variable $s masks earlier declaration in same scope at t.pl line 5.
"my" variable $s masks earlier declaration in same scope at t.pl line 10.
the quick red fox
Foo
Bar
Use of uninitialized value $s in print at t.pl line 11.

Foo

##</code><code>##

#!/tools/packarch/public/perl/5.8.8/bin/perl
use strict;
use warnings;
 
open(my $file,  "<",  "input.txt")  or die "Can't open input.txt: $!";
my $string = "icecream";
my $notfound = ""; 
while (<$file>)  
{
  if (/$string/)
  {
     print "found string $string\n";
  }
  else
  {
     $notfound = "not found";
  }
}
if ($notfound eq "not found")
{
  print "string not found\n";
}